This is the third in a series of articles on the extraction of our natural gas. The first discussed the formation of this gas. The second described the siting and drilling of your gas well.
After the vertical length of the hole has been drilled down to the black shale and across the horizontal length within the layer of shale, the rig and the support equipment are removed. Next, this black shale must be fractured by water at high pressure to release the gas. Soon, a new fleet of trucks arrives, many more than before, and eventually fills the drilling site.
Fracking
A three inch plastic collection tube is inserted to the bottom of the hole. Inside this, cylinders a dozen feet long are lowered to the bottom of the hole on a cable. Each has an array of small shaped-explosive charges. These are triggered to perforate the steel and concrete lining. Two to four cylinders are used for each stage.
Several pumper trucks are connected to the well head through a network of pipes. They pump thousands of gallons of water per minute down the hole at pressures of thousands of pounds per square inch. Sand is added to the water to hold the fractures open after the pressure is released. Chemicals are also added, for a variety of functions. First, chemicals are added to the water in a mixer truck, then sand is added in a blender truck. From there, the mixture goes to the pumps. Even these powerful pumps can only fracture the rock around the hole for a few hundred feet at a time, so the horizontal hole is fractured (fracked) in several stages, starting from the far end and working backward – for some thousands of feet. Each stage of the horizontal fracking of shale requires 500,000 gallons of water, 250 tons of sand, and thousands of gallons of various chemicals. (This is a pound of sand for every gallon of water.) Scores of water tanker trucks are necessary to provide enough water for each stage.
Much of the fracture fluid is pushed upward by the gas and flows back out of the hole. This flow-back water is collected in those same tanker trucks that supplied the water, is trucked off-site, and should be disposed of as specified in the drilling permit. The fracking has taken only a week or so, but flow-back can take weeks or even months.
Completing
The supply of gas is measured by the volume released with the valve fully open. Released gas is burned at the end of a tall pipe in a flare off. Until the pipeline is connected, gas may be flared occasionally to relieve pressure.
Each well must be connected to a pipeline before its gas can flow to customers. You will have to wait until then to receive your royalty payments, but you will get a small shut-in payment.
If there is enough gas, and once there is a pipeline, then your well is readied for production. At least two months have passed, but it can take many months or rarely years. If drillers decide to drill more horizontal holes from this site but in different directions, just the drilling could last half a year or more. The New York State Department of Environmental Conservation, which regulates drilling, encourages multi-well sites, such as the sites proposed for Hancock with six wells each.
In this final phase, the top of the collection tube is first connected to a set of pipes, valves and gages called a christmas tree, which stand four to seven feet tall. (Many are wider at the base, taper upward, and some are even painted green.) Before connecting the pipeline, a few pieces of equipment are connected from the christmas tree, such as a separator columns for any water that comes up with the gas, a water storage tank, and a flow meter. At last, the site is cleaned-up and regraded. Any water left in the reserve pit is hauled away. The plastic pit liner is folded over the rock chips, which are left in the bottom, and buried. The stockpile of soil is spread around the site and seeded with grass.
Your lease may provide that you are paid only after the gas is sold. Because the demand for gas is higher in winter, “your” gas may be stored underground for months before being sold.
Production and Plugging
Now that the well is completed, the only regular activity at the well head is emptying tanks of produced water. Occasionally, the equipment is serviced. As time goes on, the production of gas decreases – as do your royalties. After a few years, in order to increase production, the gas company may decide to refracture the shale. They might do this several times over the lifetime of this well.
The productive lifetime of a well in black shale can be decades, but eventually not enough gas can be produced to turn a profit. Then the well should be plugged by the drilling company, or by the DEC, using money that the company has previously bonded. The equipment and any recoverable tubing and piping is removed. In agricultural areas, all pipes are cut off at least 4 feet below the surface, the hole is plugged with cement and mud, and buried.
The first three articles in this series are available on franklinlocal.org. The fourth will deal with the possible effects of natural gas extraction on our local environment.